Fabric whitener

ABSTRACT

A composition for the whitening of domestic fabrics which include a nylon and/or lycra component, said composition comprising thiourea dioxide and an alkali.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a product for whitening fabric articleswhich have become discolored, in particular lingerie or underwear fabricitems made from or containing nylon which have become discolored due tocolor runs or a build up of dye during repeated washing.

It is known that white fabric items, in particular lingerie, becomediscolored with repeated washing over time, taking on a grey or dirtyblue tinge, which is regarded by the consumer as being dirty. It hasbeen found by our research that this discoloration is due in a largepart to a very slow color run from colored articles washed at the sametime and which contain non-fast dye. Often when sorting their washinginto colored and white wash loads, consumers include light blue itemsand mainly white items (but with a little color) in the white wash load.

Previously it was thought that most of the discoloration on the whitefabrics was a result of dirt becoming entrained in the white fabric.However, our research shows that a small amount of loose dye is releasedfrom the colored article in each wash and transfers to the whitearticle. The color thus builds up on repeated washing with coloredarticles. This is difficult to remove, especially if the white articleand the dye have a strong affinity for each other.

Discoloration occurs on most fabrics, but is particularly a problem onnylon and lycra (which each have a strong affinity for non-fast dyes)and to a lesser extent cotton and polyester. There are no productsavailable which will restore this lost whiteness to articles containingnylon and/or lycra which have started to discolor. White lingerie islargely made up from a combination of these materials and is thereforeprone to this form of discoloration over time, turning a blue or greycolor. In some cases this can occur very quickly if the light washingload generally includes a large amount of non-fast dye, in particularfrom blue articles, in the machine.

Some products on the market attempt to prevent non-fast dye fromdiscoloring light or white items in the first place by using bleaches ordye scavengers. The object of these products is to pick up any loose dyein the wash before it becomes attached to the white item. Alternatively,they may effectively bleach the non-fast dye while it is loose in thewater so that it loses its color before it attaches itself to a lightitem. These dye scavenger products do not treat items which havepreviously become discolored.

There are products on the market designed to remove color runs, butthese products are only effective on certain fabric types; they are noteffective on nylon and lycra which are major constituents of lingerieand underwear. It is also not readily understood by the consumer thatthe grey discoloration is from a run of colored dye because this buildsup slowly over time.

Industrially, dye removal is operated under very severe conditions.Reducing agents are used at their boiling point, usually with causticsoda, to bleach the fabric to remove the color. Very occasionally,chlorine bleach may be used to strip out dye, but this may damage thestructure of the fabric material permanently and can subsequently causewhite fabric to have a yellow or orange hue. This discoloration can notbe treated as the chemical structure of the fabric has been altered.

Dilute chlorine bleach solutions can also be used domestically to treatlight or white items, but again this can irreparably damage the chemicalstructure of the fabric.

The present invention seeks to overcome the problems of the prior art. Afirst object is to provide a product which restores the whiteness indiscolored nylon and/or lycra fabrics in a domestic environment.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a composition forthe whitening of domestic fabrics which include a nylon and/or lycracomponent, said composition comprising thiourea dioxide(formamidesulphinic acid) and an alkali. The invention is particularlysuitable for use in whitening nylon and lycra which are perceived asbeing difficult to treat using conventional materials. Among domesticgarments which can be treated using the compositions of the presentinvention are lingerie and underwear items which usually include a nylonelement.

The thiourea dioxide operates as a reducing agent and is preferablypresent at a concentration of at least 2.5% on weight of fabric, morepreferably 2.5 to 10%, and most preferably 6 to 10%. Surprisingly,thiourea dioxide has been shown to give substantially superior resultswhen compared to other reducing agents such as sodium hydrosulphite andsodium formaldhydesulphoxylate, even when much higher concentrations ofthese other materials are used.

Preferably, the alkali is present in an amount to give a pH greater than7.0, more preferably greater than 8.0, and most preferably in the range8.5-10.0.

Preferably, the treatment is carried out at a temperature of greaterthan 40° C., more preferably in the range 50 to 65° C., and mostpreferably at approximately 60° C.

Optionally, the composition further comprises a dye scavenger component.These compounds are often referred to as dye transfer inhibitors (DTI),and pick up loose or non-fast dye in the solution to prevent most or allof the loose dye from becoming attached to the light fabrics at all.These compounds do not generally remove dye which has previously becomepermanently attached to the fabrics. Preferably the dye scavenger isselected from the list of polyvinylpyrrolidone andpoly(4-vinylpyridinium N-oxide), most preferably poly(4-vinylpyridiniumN-oxide). Preferably this is present at a concentration of greater than0.2% on weight of fabric, more preferably at a concentration ofapproximately 0.4%.

The invention also extends to a method of treatment to removediscoloration from domestic white fabric articles which include a nylonand/or lycra component, in which the fabric article is treated with acomposition including thiourea dioxide and an alkali. A preferredtreatment method comprises the steps of soaking the article in asolution of the composition of the present invention, followed by awater rinse and a conventional washing cycle. Other preferred featuresof the composition set out above apply equally to the method of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention may be put into practice in a number of differentways and various embodiments will described here in further detail byway of non-limiting example.

Samples of white nylon were stained with various different color dyes bysoaking them in a solution of the dye. In all instances 0.05 g dye perkg of nylon were dissolved in water and the fabric was treated with thissolution at 60° C. in a washing machine cycle, and then spun and driedat ambient temperature to stain the fabric. Once treated, the discoloredsamples were measured for “whiteness” using a Datamaster V.2.3spectrophotometer. These results are in the form of delta E (ΔE), orcolor strength, and original white fabric produces a reading of 0.00.The lower the ΔE value, the whiter the fabric.

C.I. Direct Red 81 was the primary dye used, as it was easier to see thevisual effects of the treatments with a red dye than with a blue dye.However, tests were also conducted using C.I. Direct Blue 251 and C.I.Direct Yellow 27.

The dyed samples were treated with a variety of products under theconditions set out below. The conditions were the same for all examplesunless otherwise indicated.

250 g of stained fabric was treated in 7.5 litres of water whichincluded the indicated amount of the active component and with aninitial pH of 9.9 unless otherwise indicated to the contrary. The waterwas initially at 60° C. and the treatment lasted 30 minutes with thesolution being stirred initially and then occasionally over the 30minutes. There was no external heating of the solution over the 30minutes, so the solution cooled during the treatment. After removal fromthe treatment solution the fabric sample was rinsed under cold tapwater, and then washed in a normal washing cycle at 40° C. using astandard detergent. In the following tables, “o.w.f.” is an abbreviationfor “on weight of fabric”

EXAMPLE 1

Effect of Concentration of Thiourea Dioxide at a pH of 9.9.

Samples were treated with different concentrations of thiourea dioxideas the active component and the results are given in table 1 below.TABLE 1 Treatment Δ E Stained, untreated 16.05 Thiourea dioxide 10%o.w.f 6.44 Thiourea dioxide 5% o.w.f 6.11 Thiourea dioxide 2.5% o.w.f6.91 Thiourea dioxide 1.25% o.w.f 11.66 Thiourea dioxide 0.63% o.w.f13.18

From these results it can be seen that a minimum of 2.5% o.w.f thioureadioxide is desirable to obtain significant whitening of the nylon. Itcan also be seen that increasing the concentration of the thioureadioxide further does not significantly increase performance.

EXAMPLE 2

Effect of pH on Thiourea Dioxide.

Samples were treated with thiourea dioxide at a concentration of 10%o.w.f. at different pH by altering the concentration of alkali presentin the solution. The results are given in table 2 below. TABLE 2 pH Δ EStained, untreated 16.05 pH 9.9 6.44 pH 9.0 5.21 pH 8.0 8.98 pH 7.0 8.77pH 5.0 11.34

From these results it can be seen that the treatment is more effectiveunder alkaline conditions, and in particular at a pH around 9.0.

EXAMPLE 3

Effect of Temperature

Samples were treated with thiourea dioxide (10% o.w.f.) at a range oftemperatures and the results are given in table 3 below. TABLE 3Temperature Δ E Stained, untreated 16.05 40° C. 12.99 50° C. 8.07 60° C.6.44 80° C. 0.95 95° C. 0.35

From these results it can be seen that a treatment temperature of atleast around 50° C. is required to achieve significant whitening of thenylon. Treatment at higher temperatures produce even greater effects,but some care may be required if domestic treatment is to be carried outat these higher temperatures.

Comparative Example 1

Effect of Concentration of Sodium Hydrosulphite.

The samples were treated with sodium hydrosulphite as active componentin place of thiourea dioxide under the same conditions. The results areset out in table 4 below. TABLE 4 Treatment Δ E Stained, untreated 16.05sodium hydrosulphite 20% o.w.f. 7.11 sodium hydrosulphite 10% o.w.f.7.46 sodium hydrosulphite 5% o.w.f. 10.85 sodium hydrosulphite 2.5%o.w.f. 11.96 sodium hydrosulphite 1.25% o.w.f. 12.60

From these results it can be seen that even at a concentration of 20%o.w.f. sodium hydrosulphite, the nylon is not as white as when treatedwith 2.5% o.w.f. thiourea dioxide.

Comparative Example 2

Effect of poly (4-vinylpyridinium N-oxide) (a Dye Transfer Inhibitor) asa Whitener.

The samples were treated with poly (4-vinylpyridinium N-oxide)(hereinafter referred to as DTI) as active component in place ofthiourea dioxide under the same conditions. The results are set out intable 5 below. TABLE 5 Treatment Δ E Stained, untreated 16.05 DTI 0.4%o.w.f. 14.40 DTI 0.2% o.w.f. 15.18 DTI 0.1% o.w.f. 17.48 DTI 0.05%o.w.f. 20.22 DTI 0.025% o.w.f. 20.17

From these results it can be seen that DTI has little effect on its ownas a whitener, although at concentrations above 0.2% o.w.f. some mildwhitening effect can be seen.

EXAMPLE 4

Effect of Combinations of Thiourea Dioxide and DTI at a pH of 9.9.

A composition including both thiourea dioxide and a dye transferinhibitor (DTI) was tested under the conditions set out above, and theresults are shown in table 6 below. TABLE 6 Treatment Δ E Stained,untreated 16.05 10% thiourea dioxide o.w.f./DTI 0.4% o.w.f. 4.60 5%thiourea dioxide o.w.f./DTI 0.2% o.w.f. 5.70 2.5% thiourea dioxideo.w.f./DTI 0.1% o.w.f. 7.50 1.25% thiourea dioxide o.w.f./DTI 0.05%o.w.f. 8.29 0.63% thiourea dioxide o.w.f./DTI 0.025% o.w.f. 12.49

From these results it can be seen that there is a synergistic effect ofthe reducing agent (thiourea dioxide) and the dye transfer inhibitorwhich produces results which are unexpectedly significantly better thanusing either component alone. For example, comparing the ΔE value fromTable 1 for 10% thiourea dioxide with that for 10% thiourea dioxide and0.4% DTI from Table 6, it can be seen that the nylon is whiter aftertreatment with the combined composition (4.6 c.f. 6.44).

Comparative Example 3

Comparison with Commercially Available Products

A number of commercially available products for domestic cleaning andtreatment which either claim to whiten fabric or to remove color runsfrom the wash liquid, thereby avoiding discoloration, were tested andcompared with a product according to the present invention. The sampleswere all treated by the same method set out above. The results are setout in table 7 below. TABLE 7 Product treatment Δ E Stained, untreated16.05 Glo-Care Rescue Colour Run Remover. 5% o.w.f. 10.92 Glo-WhiteSuper whitener. 3.4% o.w.f./Ariel 17.85 Essential 14% o.w.f. VanishTablets 8.8% o.w.f./Ariel Essential 15.44 14% o.w.f. Ace Washbooster 30%o.w.f./Ariel Essential 19.13 14% o.w.f. Ariel Essential 14% o.w.f. 13.88Dylon Lingerie Whitener 10% o.w.f. thiourea 4.60 dioxide/0.4% o.w.f. DTI

It is clear that the commercially available products do not workeffectively on nylon. Indeed, the most effective (Glo-Care Rescue),which is based on sodium hydrosulphite, states that it is not suitablefor use on nylon. The present invention whitens nylon (amongst otherfabrics) as shown in the table above.

EXAMPLE 5

Samples were discolored with C.I. Direct Blue 251 instead of C.I. DirectRed 81, and the results of treatment with a variety of compositions areset out in table 8 below. TABLE 8 Treatment Δ E Stained, untreated 7.15Effect of sodium hydrosulphite (20% o.w.f.) 1.87 Effect of thioureadioxide (10% o.w.f.) 1.71 Effect of sodium hypochlorite (40% o.w.f. of14.55 15% available chlorine)

It will be apparent from these results that treatment with thioureadioxide under alkaline conditions significantly whitens the nylon.Treatment with sodium hypochlorite (household chlorine bleach) removesthe dye, but discolors the nylon-hence the high color strength. Asindicated above, the use of chlorine also damages the underlyingstructure of the fabric.

EXAMPLE 6

Samples were discolored with C.I. Direct Yellow 27 instead of C.I.Direct Red 81, and the results of treatment with a variety ofcompositions are set out in table 9 below. TABLE 9 Treatment Δ EStained, untreated 13.87 Effect of sodium hydrosulphite (20% o.w.f.)13.86 Effect of thiourea dioxide (10% o.w.f.) 11.25 Combination ofthiourea dioxide/DTI (10% 9.36 o.w.f./0.4% o.w.f.)

Again, it will be apparent from the results that treatment with thioureadioxide under alkaline conditions significantly whitens the nylon. It isalso apparent that thiourea dioxide again produces a significantlybetter performance than sodium hydrosulphite, even at half theconcentration. Further, it can be seen that the addition of DTI to thethiourea dioxide produces an even greater effect than thiourea dioxidealone, highlighting the synergy between the components.

These examples are not limiting and it will be apparent to a personskilled in the art that the results from the experiments described aboveare not dependent upon the dye which discolors the white fabric.Therefore, it is clear that the composition of the present invention isgenerally applicable to treatment in a domestic environment of whitefabrics which include a nylon and/or lycra component.

Although the foregoing description of the present invention has beenshown and described with reference to particular embodiments andapplications thereof, it has been presented for purposes of illustrationand description and is not intended to be exhaustive or to limit theinvention to the particular embodiments and applications disclosed. Itwill be apparent to those having ordinary skill in the art that a numberof changes, modifications, variations, or alterations to the inventionas described herein may be made, none of which depart from the spirit orscope of the present invention. The particular embodiments andapplications were chosen and described to provide the best illustrationof the principles of the invention and its practical application tothereby enable one of ordinary skill in the art to utilize the inventionin various embodiments and with various modifications as are suited tothe particular use contemplated. All such changes, modifications,variations, and alterations should therefore be seen as being within thescope of the present invention as determined by the appended claims wheninterpreted in accordance with the breadth to which they are fairly,legally, and equitably entitled.

1. A composition for the whitening of domestic fabrics which include anylon and/or lycra component, said composition comprising thioureadioxide and an alkali.
 2. A composition as defined in claim 1, in whichthe thiourea dioxide is present at a concentration of at least 2.5%o.w.f.
 3. A composition as defined in claim 2, in which the thioureadioxide is present at a concentration of between 2.5 and 10% o.w.f.
 4. Acomposition as defined in claim 1, in which the pH is greater than 7.0.5. A composition as defined in claim 4, wherein the pH of saidcomposition is greater than 8.0.
 6. A composition as defined in claim 1,in which the composition is used at an initial temperature of greaterthan 40° C.
 7. A composition as defined in claim 6, in which the initialtemperature is in the range of 50-65° C., preferably 60° C.
 8. Acomposition as defined in claim 1, in which the composition furthercomprises a dye scavenger component.
 9. A composition as defined inclaim 8, in which the dye scavenger component is one of the groupconsisting of polyvinylpyrrolidone and poly(4-vinylpyridinium N-oxide).10. A composition as defined in claim 9, in which the dye scavengercomponent is poly(4-vinylpyridinium N-oxide).
 11. A composition asdefined in claim 10, in which the poly(4-vinylpyridinium N-oxide) ispresent at a concentration of greater than 0.2% o.w.f., preferably about0.4% o.w.f.
 12. A method of treatment to remove discoloration fromdomestic white fabric articles which include a nylon and/or lycracomponent, in which the fabric article is treated with a composition asdefined in claim
 1. 13. A method of treatment as defined in claim 12, inwhich the treatment comprises the steps of soaking the article in asolution of the composition as defined in claim 1, followed by a waterrinse and a conventional washing cycle.
 14. A composition as defined inclaim 3, wherein said thiourea dioxide is present at a concentration ofbetween approximately 6 and 10% o.w.f.
 15. A composition as defined inclaim 5, wherein the pH of said composition is in the range ofapproximately 8.5 to 10.0.
 16. A composition for the whitening of adomestic fabric which includes a nylon and/or a lycra component, whereinthe fabric is discolored having a initial color strength value, saidsystem comprising: an alkaline thiourea dioxide component capable ofwhitening the fabric to a first color strength value of the fabric belowthe initial color strength value of the fabric at an effective amount ofthiourea dioxide component; and a dye scavenger component capable ofwhitening the fabric to a second color strength value below the initialcolor strength value of the fabric at an effective amount of dyescavenger component; wherein the combination of the effective amounts ofthiourea dioxide component and dye scavenger component whitens thefabric to a color strength value below the initial color strength valueof the fabric, the first color strength value, and the second colorstrength value.
 17. A composition as defined in claim 16, wherein the pHof the alkaline thiourea dioxide component is in the range ofapproximately 8.5 to 10.0.
 18. A composition as defined in claim 16,wherein the thiourea dioxide is present at a concentration of at leastapproximately 2.5% o.w.f.
 19. A composition as defined in claim 16,wherein the dye scavenger component is selected frompolyvinylpyrrolidone, poly(4-vinylpyridinium N-oxide), and combinationsthereof.
 20. A composition as defined in claim 16, wherein thepoly(4-vinylpyridinium N-oxide) is present at a concentration of greaterthan 0.2% o.w.f., preferably about 0.4% o.w.f.
 21. A method of treatmentto remove discoloration from domestic white fabric articles whichinclude a nylon and/or lycra component and have an initial colorstrength value, said method comprising: providing an effective amount ofthiourea dioxide in an aqueous medium in combination with an effectiveamount of a dye scavenger component; and contacting the fabric with thecombination under alkaline conditions.
 22. A method as defined in claim21, wherein the thiourea dioxide is present at a concentration of atleast approximately 2.5% o.w.f.
 23. A method as defined in claim 21,wherein the dye scavenger component is selected frompolyvinylpyrrolidone, poly(4-vinylpyridinium N-oxide) and combinationsthereof.
 24. A method as defined in claim 21, wherein the fabric iscontacted with the combination at a pH greater than 7.0.
 25. A method asdefined in claim 21, wherein contacting the fabric comprises soaking thefabric until a color strength value below the initial color strengthvalue is achieved.
 26. A composition for the whitening of domesticfabrics which include a nylon and/or lycra component, wherein the fabricis discolored having a initial color strength value, said compositioncomprising: thiourea dioxide and an alkali in an aqueous medium; whereinsaid thiourea dioxide is present in an amount effective to reduce thecolor strength value of the fabric below the initial color strengthvalue of the fabric.